Electron-beam gun with adjustable filament baffle



y 25, 1967 w. cs. COLEMAN ETAL 3,333,136

ELECTRON-BEAM GUN WITH ADJUSTABLE FTLAMENT RAFFLE Filed March 25, 1965 IN VE N TORS. L avail/ xam 8 A f torn ey United States Patent 3,333,136 ELECTRON-BEAM GUN WITH ADJUSTABLE FILAMENT BAFFLE William G. Coleman, South Gate, and John Stugart, J12,

West Covina, Califi, assignors to United States Steel Corporation, a corporation of Delaware Filed Mar. 25, 1965, Ser. No. 442,580 Claims. ((11. 313-146) ABSTRACT OF THE DISCLOSURE An electron-beam gun composed of spaced side walls between which a high-voltage platform is mounted on spaced terminals. A thermionic emitter is stretched between these terminals. The platform is insulatingly clamped to a beam extending between the side walls. A cylindrical bathe open on one side partly surrounds the emitter and is adjustably supported on the platform.

This invention relates to apparatus for generating a beam of electrons .for heating by bombardment and in particular, to an electron-beam gun compact in size which may be designed for a high current output.

Electron-beam guns have been known and used in various industrial applications for some time. Some of these applications present special problems. A typical application is the heating of the surface of a bath of molten metal, such as aluminum in a vacuum chamber, to form an ascending cloud of vapor for condensation on a substrate, metallic or non-metallic, traveling thereabove, whereby to deposit a metallic coating on the substrate. In scaling up trial installations of this type to commercial size, the first problem is the great increase in electrongenerating capacity required in order to vaporize coating metal at a rate adequate for coating wide strip traveling at high speed, say 1500 f.p.m. Other requirements for guns used in vaporizing metal include the production of a beam uniformly spread over a substantial area, the ability to operate for long periods, small size and a location out of the metal-vapor path.

We have invented a novel electron-beam gun which fully satisfies the foregoing requirements and possesses other important advantages as well. In a present preferred form of our gun, we provide a grounded bottom plate with spaced upstanding side walls and, by a transverse beam engaging the walls, we clamp to the base, between electrical insulators, a high-voltage platform. Leaf springs upstanding above the platform rcmovably support an electron emitter, e.g., a filament of refractory wire adapted to be heated to incandescence by the passage of current therethrough. A cylindrical bafile or enclosure for the filament is adjustably mounted on the platform and shields or accelerating anodes are similarly mounted on the side walls projecting partly over the enclosure. The entire gun, of course, is enclosed within a suitable vacuum chamber for operation.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawings:

FIGURE 1 is a central longitudinal section through our gun showing parts in elevation; and

FIGURE 2 is a transverse section taken along the plane of line IIII of FIGURE 1.

, Referring now in detail to the drawings, our gun, designated generally at 10, is mounted on a base 11 common to related apparatus, such as a crucible for holding the molten metal to be vaporized. The gun has a bottom 3,333,136 Patented July 25, 1967 plate 12 and side walls 13 upstanding thereon. The bottom plate and side walls are grounded by contact with base 11 and the bottom plate is slotted at its ends to admit conducting terminal straps 14 and 15 extending up wardly between the side walls free of contact therewith or with the bottom plate. A high-voltage platform 16 is secured to strap 15 and extends laterally therefrom toward strap 14. The latter has a yoke-shaped portion 14a. Alined shielded insulators 17 are fitted between the latter and the free end of platform 16 and secured thereto by a through bolt 18. Insulators 17 comprise a block or stud 19 of refractory insulating material such as fused alumina, with opposed, partially telescoped metal shielding caps 20 and 21 on opposite ends thereof.

A transverse bar 22 extends as a beam between side walls 13 and through holes 23 therein. By means of a screw plug 24- threaded through beam 22, platform 16 is rigidly clamped between lower insulators 25 resting on a spacer block 26 on plate 12, and an upper insulator 27. Insulators 25 and 27 are similar in structure to insulators 17.

Leaf springs 28 of electrically conducting material extending upwardly from straps 14 and 15 have studs 29 thereon. An electron emitter 30' in the form of a helical coil or a zig-zag length of refractory wire, e.g., tungsten, has sockets 31 at its ends adapted to receive studs 29. Electric current for heating the emitter is circulated through the coil by connections to straps 14 and 15 and the electron emitter is maintained as a cathode by a high negative voltage applied to strap 15. An auxiliary support 32 for the mid-point of the emitter extends from an insulator 33 mounted on portion 14a of strap 14. Insulator 33 is similar to insulators 17.

The emission of electrons by filament 30 when heated is aided, and the stream of emitted electrons is shaped by accelerating anode plates or shields 34 and 34a adjustably secured to side plates 13. The emitted beam is further constriction and shaped by a cylindrical bafile 35 open throughout its length on the upper side. A hole 35a in the bafile admits the emitter support 32. Bathe 35 is carried by cradles 36 upstanding on blocks 37. Each block fits loosely within a box 38 on platform 16, and rests on shaft 39 extending therethrough with eccentrics at the ends thereof. Each shaft 39 extends outwardly through a yoke 40 partially embracing the box and provided with a clamping screw 41. Clamping screws 42 threaded through the sides of each box adjustably secure the block contained therein. It will be evident that turning shafts 39 effects vertical adjustment of bafile 35 while screws 4-2 permit lateral adjustment. One end of each shaft 39 is slotted so it may be turned by a screw driver and side plates 13 have access holes 43 therein, alined with shaft 39 and screws 42.

As stated, the electron-beam gun of our invention has many advantages besides high capicity, compactness and the ability to deliver a beam spread uniformly over a substantial area for heating a surface. The gun structure is modular, Le, a plurality of units such as that illustrated may be assembled in end-to-end relation to cover almost any desired length of crucible to cover the full width of strip to be coated. The beam of electrons ascending from the emitter may be easily deflected by a magnetic field onto the surface of the metal to be vaporized. Thus the gun may be located where unwanted vapor condensation thereon is a minimum and long operating periods are thus obtainable without removal of the gun for maintenance. The leaf springs for holding the emitter permit elongation and contraction thereof without distortion, as well as easy replacement of the filament. The baffle 35 causes the emitter to produce a dense beam of electrons with a high voltage gradient to the accelerata ing anodes 34 and 34a. The battle also protects the anodes from excessive bombardment.

Although we have disclosed herein the preferred embodiment of our invention, we intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention as set forth in the claims.

We claim:

1. An electron-beam gun comprising a pair of spaced terminal straps, an electron emitter mounted on said straps and extending thercbetween, a high-voltage platform secured to one of said straps and extending toward the other but terminating short of the latter, a trough-shaped bafile disposed substantially coaxially with said emitter, and means adjustably mounting said bafiie on said plat form.

2. Apparatus as defined in claim 1, characterized by a bottom plate having recesses therein through which said straps project and means clamping said platform to said plate in insulated relation thereto.

3. Apparatus as defined in claim 2, characterized by side walls upstanding on said plate, said last-mentioned means including a cross beam extending between said walls and a screw threaded therein.

4. Apparatus as defined in claim 1, characterized by said other strap having a yoke-shaped portion therein and insulators between said portion and said platform.

5. Apparatus as defined in claim 1, characterized by leaf springs attached to said strap, said emitter being mounted on said leaf springs.

Apparatus as defined in claim 5, characterized by detachable stud-and-socket connections between said springs and said emitter.

7. Apparatus as defined in claim 1, characterized by said last-mentioned means including a pair of saddles spaced along said shield and means supporting said saddies for movement from and to said platform.

8. Apparatus as defined in claim 7, characterized by said supporting means including a pair of boxes and blocks fitting loosely therein.

9. Apparatus as defined in claim 1, characterized by said last-mentioned means including a pair of saddles spaced along said shield and means supporting said saddles for movement laterally of said platform.

19. Apparatus as defined in claim 9, characterized by said supporting means including a pair of boxes and blocks fitting loosely therein.

No references cited.

JAMES 'W. LAWRENCE, Primary Examiner.

V. LAFRANCHI, Assistant Examiner. 

1. AN ELECTRON-BEAM GUN COMPRISING A PAIR OF SPACED TERMINAL STRAPS, AN ELECTRON EMITTER MOUNTED ON SAID STRAPS AND EXTENDING THEREBETWEEN, A HIGH-VOLTAGE PLATFORM SECURED TO ONE OF SAID STRAPS AND EXTENDING TOWARD THE OTHER BUT TERMINATING SHORT OF THE LATTER, A TROUGH-SHAPED BAFFLE DISPOSED SUBSTANTIALLY COAXIALLY WITH SAID EMITTER, AND MEANS ADJUSTABLY MOUNTING SAID BAFFLE ON SAID PLATFORM. 